1. Technical Field
The disclosure relates to a non-volatile memory and a manufacturing method thereof, and particularly relates to a non-volatile memory that prevents a second bit effect and a manufacturing method thereof.
2. Related Art
The non-volatile memory is characterized by maintaining the stored data even when the power is down, and has thus become a mandatory device in many electronic products for providing normal operation of the electronic products when booted. In particular, flash memory is a type of non-volatile memory that allows multiple times of programming, reading and erasing operations. With these advantages, flash memory has become one of the most widely adopted memory devices for personal computers and electronic equipments.
Nitride-based flash memory is a common non-volatile memory nowadays. In a nitride-based flash memory, a two-bit data is stored by using a charge trapping structure formed of an oxide-nitride-oxide layer (the well-known ONO layer). Generally speaking, the two-bit data may be respectively stored at the left side (left bit) and the right side (right bit) of the nitride layer in the charge trapping structure.
However, there is a second bit effect in the nitride-based flash memory. Namely, a reading operation to the left bit is influenced by the right bit, whereas a reading operation to the right bit is influenced by the left bit. In addition, as the memory size reduces, the channel length is reduced accordingly, rendering an even more significant influence of the second bit effect. Therefore, the operation window and device performance of the memory are influenced.